Image transfer process

ABSTRACT

A method of transferring insulating image material containing a static charge from an image bearing surface to an electrically non-conductive image receiving surface by means of coulombic attraction and the rearrangement of electrical charges.

United States Patent 1 1 1111 3,837,883

Menz 1 ]*Sept. 24, 1974 IMAGE TRANSFER PROCESS 3,512,968 5/1970 Tulagin 96/l.4 x 3,663,219 5/1972 Takahashi l 96/1.4 [75] Inventor: Elsie L. Menz, Rochester, NY. 3,706,553 12/1972 Menz 96/14 73 AssigneeI Xerox Corporation Rochester, 3,729,334 4/1973 Snelling 96/].4 X

[ Notice: The portion of the term of this FOREIGN PATENTS OR APPLICATIONS Patentsubsequem to 1989 38-19 790 9/1963 Japan 96/1 4 has been dlsclalmed- 42-21,;373 10/1967 Japan 96/l.4 [22] Filed: Oct. 30, 1972 [21] Appl. No.: 302,367 Primary ExaminerR0land E. Martin, Jr.

Related US. Application Data gzgaggg giigggg r Ralabate; David [62] Division Of Ser. N0. 886,838, Dec. 22, 1969, Pat. NO.

52 US. Cl 117/175, 96/1.4, 117/37 LE, [57] ABSTRACT 3118/638 A method of transferring insulating image material [51] Int. CLf. $70 g 13/1}; Containing a Static Charge from an image bearing Sun [58] F'eld 0 9 11 37 face to an electrically non-conductive image receiving surface by means of coulombic attraction and the re- [56] References cued arrangement of electrical charges.

UNITED STATES PATENTS 3,384,488 5/1968 Tulagin et al 96/15 X 7 Claims, 2 Drawing Figures IMAGE TRANSFER PROCESS This is a division, of application Ser. No. 886,838, filed Dec. 22, 1969 now US. Pat. No. 3,706,553.

BACKGROUND OF THE INVENTION The present invention relates in general to the transfer of images from an image bearing surface to an image receiving surface and more particularly to a method for accomplishing such transfer by means of a rearrangement of static electric charges and coulombic attraction Various imaging processes are known wherein a thin film of material is deposited on a substrate or image bearing surface to provide a contrast to said surface in image configuration. Due to the process steps employed in producing such images, the substrate on which the image is first formed is, in some cases, not the substrate which is most durable, useful or desirable.

One such imaging process which provides images comprising a thin film or layer of an insulating or semiconductive material on a substrate is the manifold imaging process as described in copending application Ser. No. 708,380, filed Feb. 26, 1968 now US. Pat. No. 3,707,368. In this imaging system, an imaging layer is prepared by a coating of a layer of electrically photosensitive imaging material onto a substrate. In one form the imaging layer comprises a photosensitive material such as metal-free phthalocyanine dispersed in a cohesively weak insulating or dielectric binder. This coated substrate is called the donor. When needed, the imaging layer is rendered cohesively weak. The process step of weakening the imaging layer is termed activation and in most cases the imaging layer is activated by contacting it with a swelling agent, solvent, or partial solvent for the imaging layer or by heating the layer. A receiver sheet is laid over the surface of the imaging layer and an electric field is applied across the imaging layer while it is exposed to a pattern of light and shadow representative of the image to be reproduced. Upon separation of the donor substrate or sheet and receiving sheet the imaging layer fractures along the lines defined by the pattern of light and shadow to which the imaging layer has been exposed. Part of the imaging layer is transferred to one of the sheets while the remainder is retained on the other sheet so that a positive image, that is, a duplicate of the original is produced on one sheet while a negative image is produced on the other.

In many instances, the apparatus employed to produce images by means of the manifold imaging process more conveniently uses donor and receiver sheets which are not well suited for the end use of the image. However, transferring images from one substrate to another without loss of image quality has, in the past, been difficult and required expensive and complicated machinery.

Another example of prior art imaging processes wherein the transfer of imaging material from one surface to another is employed is xerography. In most xerographic processes, an image formed by a toner on a carrier is transferred from a dielectric surface containing an electrostatic image to an image receiving substrate or medium in order to provide a usable copy. The machinery or apparatus commonly employed to perform this function is now common and notably complex.

SUMMARY OF THE INVENTION an image bearing surface to an image receiving surface without complex equipment.

Another object of this invention is to provide images of improved quality which have been transferred from an image bearing substrate to an image receiving medium.

These and other objects of this invention are apparent from the following description of the invention.

In accordance with this invention there is provided a process whereby a releasable image residing on an electrically insulating medium is transferred to an electrically non-conductive image receiving medium. Such transfer is accomplished by charging the surface of the image and the medium upon which the image resides. The thus charged image is then contacted with the nonconductive receiving medium thus forming an image transfer set. A conductive path is then provided between the outer or exposed surfaces of the image bearing medium and the image receiving medium. This is normally accomplished by contacting the exposed surfaces with conductive plates which are interconnected by a conductive wire. By means of the conductive path, both surfaces are brought to the same potential and the releasable image transfers to the image receiving medium. Upon separation of the set, there is provided a high quality image on the receiving substrate or medium. Included in the term image are portions of images and defined or artistic patterns of dielectric material on a substrate.

According to this invention, the image is electrically charged and such charge is held by the imaging material until after the transfer is accomplished. Thus, the process of this invention is particularly adapted for use in transferring images wherein the'imaging material is electrically insulating so as to maintain an electric charge for at least a brief period of time. A wide variety of insulating materials can thus be employed in the process of this invention. Insulating materials such as polyethylene, polypropylene, polyamides, polymethacrylates, polyacrylates, polyvinylchlorides, polyvinylacetates, polystyrene, polythioloxanes, chlorinated rubber, polyacrylonitrile, epoxies, phenolics, hydrocarbon resins and other natural resins such as rosin derivatives as well as mixtures and copolymers of the above materials can be employed. Particularly preferred images to be transferred according to the process of this invention are those comprising insulating materials which retain a charge and which are or can be rendered releasable. Such materials include microcrystalline waxes such as: Sunoco I290, Sunoco 5825, Sunoco 985, all available from Sun Oil Co.; Paraflint RG, available from the Moore and Munger Company; parafiin waxes such as: Sunoco 5512, Sunoco 3425, available from Sun Oil Co, Sohio Parowax, available from Standard Oil of Ohio; waxes made from hydrogenated oils such as: Capitol City 1380 wax, available from Capital City Products, Co., Columbus, Ohio; Caster Wax L-2790,

available from Baker Caster Oil Co.; Vitikote L-340, available from Duro Commodities; polyethylenes such as: Polyethylene DYJT, Polyethylene DYLT, Polyethylene DYDT, all available from Union Carbide Corp; Marlex TR 822, Marlex 1478, available from Phillips Petroleum Co.; Epolene C-l3 Epolene C-l0, available from Eastman Chemical Products, Co.; Polyethylene AC8, Polyethylene AC612, Polyethylene AC324, available from Allied Chemicals; modified styrenes such as: Piccotex 75, Piccotex I00, Piccotex 120, available from Pennsylvania Industrial Chemical; Vinylacetateethylene copolymers such as. Elvax Resin 210, Elvax Resin 420, available from E. l. duPont de Nemours & Co., Inc., Vistanex Ml-l, Vistanex L-80, available from Enjay Chemical Co.; Vinyl chloridevinyl acetate copolymers such as: Vinylite VYLF, available from Union Carbide Corp; styrene-vinyl toluene copolymers; polypropylenes; and mixtures thereof.

There has recently been discovered a photoelectrophoretic imaging method wherein electrically photosensitive pigments are employed to produce images under the influence of light and an electrical field. lmages made by this process comprise individual particles of electrically photosensitive materials which are capable of retaining an electric charge. Such a process is more fully described in U. S. Pat. No. 3,384,565 which is incorporated herein by reference. Images produced in accordance with the process described in the patent can be transferred by the method of this invention.

The materials employed to produce images by means of the manifold imaging process are more fully described in copending application Ser. No. 708,380 filed Feb. 8, 1968 which description is incorporated herein by reference. Both of the above mentioned imaging processes employ electrically photosensitive materials which are also an insulating material capable of retaining a charge and thus images produced by such processes may be transferred from an image bearing medium to an image receiving medium in accordance with the process of this invention. On the other hand, insulating imaging materials which do not contain electrically photosensitive materials may also be transferred in accordance with this invention.

The surface of the insulating image material and the supporting surface of the image bearing medium are electrically charged to the extent required to transfer the image. The amount of charge will vary depending in part upon the dielectric constant, polarity of the charge and thickness of the image material. It will also vary depending upon the dielectric constant and thickness of the image bearing and image receiving media. When employing a material exhibiting an extremely high dielectric constant, lower voltages can be employed such as from about 200 to about 400 volts. Alternatively, if materials exhibiting very low dielectric constant are employed, higher voltages are employed ranging up to an amount less than the electrical breakdown strength of the image bearing medium.

In general atransfer voltage is applied across the image material and the image receiving medium. Such voltage has a minimum value which varies with different materials and must exist in order to effect transfer.

In general, the transfer voltage is calculated accord ing to the following formula:

V VL l L/ r, d/ l: r/ rll where V, a voltage constant for the image material K dielectric constant of the image material K,, I dielectric constant of the image bearing substrate K dielectric constant of the image receiving medium D thickness of image bearing medium 0,. thickness of image receiving medium D thickness of image material In a case wherein the image bearing medium and the image receiving medium each are 1 mil in thickness and have equal dielectric constants of 3.25, the dielectric constant of the image material is 5 and is 02 mils thick, the calculated transfer voltage is 4.000 volts where the image material voltage constant is 240 volts.

Where the image is not releasable from the image bearing medium, it is desirable to include an activation step in the process of this invention. The activation step may take many forms such as heating the imaging layer thus reducing the adhesion or applying a substance to the surface of the imaging material or including a substance in the imaging material which substance lowers the adhesive strength of the imaging material with re spect to the image bearing medium. The substance so employed is termed an activator." Preferably, the activator should have a high resistivity so as to prevent electrical breakdown of the transfer set. Accordingly, it will generally be found to be desirable to purify commercial grades of activators so as to remove impurities which might impart a higher level of conductivity. This may be accomplished by running the fluids through a clay column or by employing any other suitable purification technique. Generally speaking, the activator may consist of any suitable material having the aforementioned properties. For purposes of this specification and the appended claims, the term activator shall be understood to include not only materials which are conventionally termed solvents but also those which are partial solvents. swelling agents or softening agents for the imaging material. The activator can be applied at any convenient point in the process prior to separation of the sandwich.

It is generally preferable that the activator have a relatively low boiling point so that fixing of the image on the image receiving medium can be accomplished upon evaporation of the activator. It is desirable that fixing of the image be accomplished quickly with mild heating at most. It is to be understood, however, that the invention is not limited to the use of these relatively volatile activators. In fact, very high boiling point non-volatile activators including silicone oils such as dirnethylpolysiloxanes and very high boiling point long chain aliphatic hydrocarbon oils ordinarily used as transformer oils such as Wemco-C transformer oil, available from Westinghouse Electric Co., have also been successfully utilized in the imaging process. Although these less volatile activators do not dry off by evaporation, image fixing can be accomplished by contacting the image with an absorbent sheet such as paper which absorbs the activator fluid. In short, any suitable volatile or nonvolatile activator may be employed. Typical activators include Sohio Odorless Solvent 3440, an aliphatic (kerosene) hydrocarbon fraction, available from Standard Oil Co. of Ohio, carbon tetrachloride, petroleum ether, Freon 214 (tetrafluorotetrachloropropane), other halogenated perchloroethylene, trichloromonofluoromethane, trichlorotrifluoroethane, trichlorotrifluoroethane, ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran, ethyleneglycol monoethyl ether, aromatic and aliphatic hydrocarbons such as benzene, toluene, xylene, hexane, cyclohexane, gasoline, mineral spirits and white mineral oil, vegetable oils such as coconut oil, babussu oil, palm oil, olive oil, castor oil, peanut oil and neatsfoot oil, decane, dodecane and mixtures thereof. Sohio Odorless Solvent 3440 is preferred because it is odorless, nontoxic and has a relatively high flash point.

The image bearing medium useful in the process of this invention is one which retains an electric charge for at least a short period of time and are described herein as electrically insulating. While many nonconductive materials usable as image receiving media can be classified as insulating, materials useful as image bearing media have greater electrical resistance and are thus termed electrically insulating. Typically insulating materials have a resisitivity above about l0 ohm-cms at normal temperatures. Typical examples of such materials include polyethylene, polypropylene, polyethylene terephthalate, cellulose acetate, paper, plastic coated paper such as polyethylene coated paper, vinyl chloride-vinylidene chloride copolymers and mixtures thereof. Mylar (a polyester formed by the condensation reaction between ethylene glycol and terephalic acid available from E. I. duPont de Nemours & Co., Inc.) is preferred because of its durability and excellent insulative properties.

The image receiving medium useful in the process of this invention may comprise any suitable electrically non-conductive material. In the specification and claims non-conductive is intended to mean those materials having a resistivity greater than about ohmcms at normal temperatures. Typical nonconductive materials include those listed above as image bearing media and, in addition, include metal impregnated plastics such as Stabilene film, available from Keuffel and Esser Co.. As stated above, according to the process of this invention, the exterior surfaces of the transfer set made up of an image bearing medium, the imaging material and an image receiving medium are brought to the same potential. The most common means of achieving such balance is by backing the image bearing medium with an electrically conductive layer and connecting the conductive layer to a similarly conductive layer which is backing the image receiving medium. The transfer set is then separated while the two conductive layers are electrically interconnected or the set can be separated after removing the conductive layers.

Static charges can be imposed upon dielectric layers by means known to the art as by contacting the image and image bearing medium with an electrically charged electrode. Alternatively, the layer may be charged using corona discharge devices such as those described in U.S. Pat. No. 2,588,699 to Carlson, U.S. Pat. No. 2,777,957 to Walkup, U.S. Pat. No. 2,885,556 to Gundlach or by using conductive rollers as described in U.S. Pat. No. 2,980,834 to Tregay et al7 or by frictional means as described in U.S. Pat. No. 2,297,691 to Carlson or other suitable apparatus.

' Also, metallic coatings on plastic substrates, rubber rendered conductive by the inclusion of a suitable material therein and the like can be employed. Conductive rubber is preferred because of its flexibility. Transparent conductive electrodes such as tin oxide coated glass may be employed but are not required as the transfer of the image does not require light. Obviously, if photoconductive material is employed in the process the electrical charge may be lost if operated in the presence of light.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved method of transferring images will become apparent upon consideration of the detailed disclosure of the invention especially when taken in conjunction with the accompanying drawings wherein:

FIG. 1a is an expanded side sectional view of an image transfer set prior to balancing the potential of the exposed surfaces of the set.

FIG. lb is an expanded side sectional view of an image transfer set after the potential of the exposed surfaces of the set has been balanced resulting in the transfer of the image.

DETAILED DECRIPTION OF THE DRAWINGS While FIGS. 1a and 1b are expanded in order to facilitate the explanation of the process of this invention, it is to be understood that in actual operation the elements of the image transfer sandwich are in contact with each other in the order shown in FIGS. 1a and 1b.

In FIG. la there is provided releasable imaging material 2 sandwiched between electrically insulating image bearing medium 4 and electrically non-conductive image receiving medium 6. The sandwich resides between conductive layers 8 and 10. Prior to being incorporated into the set, imaging material 2 and medium 4 have been electrically charged positive with respect to the upper surface of image bearing medium 4 which has been charged negative. Referring now to FIG. lb, when image transfer is desired, an electrical connection is made between conductive layer 8 and conductive layers 10 by means of wire 12 through switch 14. FIG. llb illustrates the imaging material 2 adhering to the image receiving medium 6 leaving image hearing medium 4 free of imaging material.

DESCRIPTION OF PREFERRED EMBODIMENTS The following examples further specifically illustrate the present invention. The examples below are intended to illustrate various preferred embodiments of the image transfer process of this invention. The parts and percentages are by weight unless otherwise indicated.

EXAMPLES IIV There is first prepared images comprising a dielectric material which retains an electric charge by means of the manifold imaging process as follows:

A commercial, metal-free phthalocyanine is first purifled by acetone extraction to remove organic impurities. Since this extraction step yields the less sensitive beta crystalline form, the x-form is obtained by the procedure described in Example I of U.S. Pat. No. 3,357,989. The x-form phthalocyanine thus produced is used to prepare the imaging layer according to the following procedure: grams of Sunoco 1290, a microcrystalline wax with a melting point of 178F. is dissolved in 100 cc. of reagent grade petroleum ether heated to 50C. and quenched by immersing the container in cold water to form small wax crystals. Five grams of the purified and milled phthalocyanine produced according to the above procedure are then added to the wax paste along with one-half pint of clean porcelain balls in a 1 pint mill jar. This formulation is then ball milled in darkness for 3 /2 hours at 70 rpm. and after milling cc. of Sohio Solvent 3440 is added to the paste. This paste is then coated in subdued green light on a 1 mil Mylar sheet with a No. 12 wire-wound drawdown rod which produces a 2.5 micron thick coat ing (Example 1) after drying. The same paste is also applied on three other Mylar sheets with a No. 8 drawdown rod to produce a coating thickness of 1 /2 microns (Example II), with a No. 24 rod to produce a coating thickness of 5 microns (Example Ill) and a No. 36 rod to produce a coating thickness of 7 /2 microns (Example IV). Each of these coatings is then heated to about 140F. in darkness in order to dry it. Then the coated donors are placed on the tin oxide surface of NESA glass plates with their coatings facing away from the tin oxide. A receiver sheet also of 1 mil thick Mylar is then placed on the coated surface of each donor. Then a sheet of black, electrically conductive paper is placed over the receiver sheet to form the complete manifold set. The receiver sheet is then lifted up and the phthalocyanine wax layer is activated with one quick brush stroke of a wide camel s hair brush saturated with Sohio Odorless Solvent. The receiver sheet is then lowered back down and a roller is rolled slowly once over the closed manifold set with light pressure to remove excess activator. The positive terminal of an 8,000 volt dc power supply is then connected to the NESA coating in series with a 5,500 megohm resistor and the negative terminal is connected to the black opaque electrode and grounded. With the voltage applied, a white incandescent light image is projected upward through the NESA glass using a Wollensak 90 mm., f 4.5 enlarger lens with illumination of approximately footcandle applied for 0.1 second for a total incident energy of 0.25 foot-candle seconds. After exposure, the receiver sheet is peeled from the set with the potential source still connected. The small amount of activator present evaporates within a second or so after separation of the sheets yielding a pair of excellent quality images with a duplicate of the original on the donor sheet and a reversal of the original on the receiver sheet in each case.

Each of the positive images produced as described above residing on the 2 mil Mylar image-bearing medium are placed on 1 mil thick Mylar immediately after being produced. The 1 mil thick Mylar is resting upon a sheet of aluminum and a second sheet of aluminum is laid upon the Mylar image-bearing medium. A short length of 14 gauge copper wire equipped with spring clamps on each end is then attached one end to each aluminum sheet. Immediately after attaching the clips, the Mylar image bearing medium and the Mylar image receiving medium are separated by hand. Each of the four images produced as described above are transferred totally to the Mylar receiver leaving the original image bearing Mylar sheet substantially free of image material. The images on the Mylar receiver are fixed by heating the imageing material slightly to remove excess activator which was originally applied to the imaging material during their production by means of a mani fold imaging process. All of the images thus transferred retain the density and resolution of the image originally produced on the Mylar image bearing medium.

EXAMPLE V An image is first prepared by means of the photoelec trophoretic color imaging process as described in US. Pat. No. 3,384,565 by preparing an 8 percent by weight suspension including equal amounts of the following pigments: Watchung Red 8. a barium salt of l-(4'- methyl-5-chloroazobenzene-2'-sulphonic acid)-2- hydroxy-3-naphthoic acid Cl. No. 15865; Monolite Fast Blue GS, the alpha form of metal-free phthalocyanine, C.l. No. 74100: and. lcyano-2.3-phthaloyl-7.8 benzopyrrocoline as synthesized according to the first technique given for its synthesis on page 1215 of the March 5, I957 Journal ofthe American Chemica! Society in an article entitled Reactions of Naphthoquinones with Malonic Ester and its Analogs Ill 1- substituted Phthaloyl and Phthaloyl Benzopyrrocolines" by Pratt et al. These pigments are magenta, cyan and yellow respectively. This mixture, which shall be referred to as a trimix hereinafter, is coated onto a 1 mil thick Mylar sheet and prepared for imaging in ac cordance with the procedure described in copending application Ser. No. 829,698 filed June 2, 1969 which is incorporated herein by reference. The trimix is subjected to an electric field by placing the sheet pigment side up on the conductive surface of a glass plate and connecting the conductive surface of the glass plate in series with a switch, a potential source and a conductive center of a roller having a coating of baryta paper on its surface. The roller is approximately 2 inches in diameter. A full color positive photographic transparency is projected through the glass plate onto the trimix by placing the transparency between the suspension and a white light source as the roller is moved across the surface of the coated glass plate. The roller is held at a negative potential of (4,000) volts with respect to the conductive glass plate. The roller is passed over the Mylar three times and cleaned after each pass. After completion of three passes, it was found that an excel lent quality full-color image with all colors well separated was left behind on the Mylar. The electric field and exposure were both continued during the entire period of the three passes by the roller. After discontinuing the voltage on the NESA. a sheet of electrically insulating bond paper is laid over the image which is residing on the surface of the Mylar. A black rubber electrode is placed over the paper and is connected to the conductive surface of the glass plate and immediately after making the connection the paper and black rubber electrode are removed from the Mylar. The image which was formerly residing upon the Mylar adheres to the bond paper and is fixed by application of a transparent polymer coating.

EXAMPLE VI A black imaging layer useful in the manifold imaging process is prepared by combining about 5 grams of xform phthalocyanine with about 5 grams Algol Yellow 9 GC, 1,2,5 ,6-di-(C )C-diphenyl (thiazoleanthraquinone, C.l. No. 67300, available from General Dyestuffs Corporation), and about 2.8 grams of purified Watchung Red B, l-(4-methyl-5-chloro-2- sulfonic acid) azobenzene-Z-hydroxy-3-naphthoic acid, C.I. No. 15865, available from E. l. duPont de Nemours & Co., about 8 grams of Sunoco Microcrystalline Grade 5825 having an ASTM melting point of llF., available from Sun Oil Company and about 2 grams Paraflint RG, a low molecular weight paraffmic material available from the Moore & Munger Company, New York City and about 320 ml. of petroleum ether (90120C) and about 14 ml. of Sohio Odorless Solvent 3440 are placed with the mixed pigments in a glass jar containing /2 inch flint pebbles. The mixture is then milled by revolving the glass jar at about 70 rpm for about 16 hours. The mixture is then heated for approximately 2 hours at about 45C and allowed to cool to room temperature. The paste-like mixture is then coated in subdued green light on 1 mil thick Mylar by means of a No. 22 wire wound drawdown rod to produce a coating weight of about 027 grams per square foot. The thus formed imaging layer on the Mylar is employed in the manifold imaging process with a conductive aluminum sheet as a receiver. The voltage applied during imaging and subsequent separation of the donor and receiver sheets is 3.5 KV/mil. A positive image is thus produced on the Mylar and with the residual voltage on the image material and the Mylar sheet the image is contacted with a sheet of 2 mil Tedlar having a dielectric constant of 9, and backed with a conductive metal layer. The Mylar image bearing medium has a dielectric constant of 3.25. A conductive rubber sheet is laid over the Mylar and electrical contact is made with the conductive sheet backing the Tedlar. The Mylar together with the conductive rubber sheet is pulled from the Tedlar leaving the image formerly residing on the Mylar now residing on the Tedlar sheet.

EXAMPLE VII Another image is made by means of the manifold imaging process employing an imaging layer prepared as described in Example VI. A manifold set comprising a 1 mil Mylar donor sheet, the black imaging material and a 1 mil Mylar receiver is employed. The voltage employed during imaging and subsequent separation of the donor and receiver sheet is 4 KV/mil. After the production of the image, the 1 mil Mylar receiver is laid on another sheet of 1 mil Mylar which has been wetted with Sohio Odorless Solvent 3440. A conductive rubber sheet is placed on top of the Mylar bearing the image and connected to a conductive plate backing the wetted Mylar sheet. After assuring firm contact of the image with the wetted Mylar sheet, the rubber electrode and the Mylar receiver is removed leaving the image on the wetted Mylar sheet.

In all of the above Examples, a right-reading copy can be obtained by the process of this invention by employing an appropriate number of mirrors in the optical system employed to produce the image. The use of mirrors in producing the image will provide a compensating factor which produces a right-reading positive image when transferred in accordance with the process of this invention.

Although specific components and proportions have been stated in the above description of the preferred embodiments of the invention, other typical materials as listed above if suitable may be used with similar results. in addition, other materials may be used to synergize, enhance or otherwise modify the properties of the imaging material. For example, various dyes, spectral sensitizers, particles made up of two or more layers, blends of materials, complexes and electrical sensitizers such as Lewis acid may be added to the imaging material.

Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

l. A method of transferring a releasable dielectric image from an electrically insulating image bearing medium to an electrically non-conductive image receiving medium said receiving medium having a resistivity of at least 10 ohm-ems, which comprises charging the surface of said image and said image bearing medium to a transfer voltage, contacting said image with said image receiving medium, providing an electrically conductive path between the exposed surfaces of said image bearing medium and said image receiving medium by contacting each said surface with electrically conductive plates, said plates being electrically interconnected, whereby said exposed surfaces are brought to the same potential and while at said potential separating said image receiving medium from said image bearing medium.

2. The method of claim 1 further including the step of rendering said image releasable by applying thereto an activator selected from the group consisting of solvents, partial solvents, swelling agents and softening agents for said image material.

3. The method of claim I wherein the transfer voltage is in the range of from about 1,000 volts per mil to less then the electrical breakdown potential of said image bearing medium.

4. The method of claim 1 wherein the image bearing medium is a thermoplastic material.

5. The method of claim 2 wherein the activator is at least a partial solvent for said image.

6. The method of claim 1 wherein the transfer voltage is residual voltage retained from the process of producing the image.

7. The method of claim 1 wherein the image receiving medium is a thermoplastic. 

2. The method of claim 1 further including the step of rendering said image releasable by applying thereto an activator selected from the group consisting of solvents, partial solvents, swelling agents and softening agents for said image material.
 3. The method of claim 1 wherein the transfer voltage is in the range of from about 1,000 volts per mil to less then the electrical breakdown potential of said image bearing medium.
 4. The method of claim 1 wherein the image bearing medium is a thermoplastic material.
 5. The method of claim 2 wherein the activator is at least a partial solvent for said image.
 6. The method of claim 1 wherein the transfer voltage is residual voltage retained from the process of producing the image.
 7. The method of claim 1 wherein the image receiving medium is a thermoplastic. 